Few ideas are nearly as tempting as setting foot on an alien planet that can be both explored and even brought to life by technology. And as the genre of science fiction has progressed, so have our ideas of what interstellar travel and (perhaps more importantly) planetary exploration would be like. And those planets, as time has shown, have proven to be anything but static lifeless bodies rolling through space. The planets themselves just as the stories about them have changed dramatically over time even if a few specific elements remain the same.
Prospective astronauts started with travel to the moon in the classic film From Earth to the Moon. Soon entire empires sprang up and were populated with ever increasingly mysterious and strange creatures. As one small step for man was made on Mars in Mars the Angry Red Planet, Earthlings discovered a massive amoeba that threatened to claim their lives and gigantic bat-like spiders that would prove difficult to kill by even superior futuristic technology and weapons. By the time Mars reached the 1980s and was adapted to film in the Governator's science fiction film Total Recall, space travel was beginning to take on more realistic technical aspects even if the adventures themselves were far off and fantastic. And the presence of aliens was always a plot device that found itself almost universally in the scripts.
Distant planets such as Mars increasingly saw the long lost ruins of an alien civilization long destroyed by unknown means. Inhabitants were seen as mysterious and sometimes bordering on magical with their technology. The presence of an extraterrestrial warning to Earth saw quite a bit of film coverage with aliens warning the ever increasingly dangerous humans that their possession of nuclear weapons posed a threat both to their own species and to other planets around them. Just as those same words are echoed when speaking of foreign nations, the idea of a global extinction event would be a common theme in films of alien encounters on distant planets.
Rarely do we see films now where alien planets are sustainable for human life without the intervention of some sort of terra-forming project. Ridley Scott's Alien franchise saw a universe where an ever expanding human race required the use of advanced terra-forming platforms on distant planets and asteroids in order to make planets rich and habitable for human life. Gone were the days where a typical starship could happen across what Star Trek termed a "class M planet" which had oxygen at levels comfortable for humans, plantlife that thrived and could be compared to Earth, and beings inhabiting it similar to ourselves.
What does this say about our own expeditions to the stars? As our own understanding of the universe around us and the cosmic neighborhood we share with other planetary bodies, we learn that the universe is not a static one that remains the same from decade to decade - at least not our perception of it. The universe as it stands is actually a whirlwind of theories and speculation where the boundaries of the imagination are all that keep us from truly taking that next step among the stars themselves. And perhaps in time we will discover that the presence of alien life on those planets is governed the same way.